There have been conventionally known fishing reels including a magnetic seal mechanism using a magnetic fluid applied to a bearing. For instance, Japanese Patent Application Publication No. 2013-97 (the “97 Publication”) discloses a support structure of a line roller in which the line roller is rotatably supported on a supporting shaft through a bearing for guiding a fishing line to a spool. The '97 Publication also describes a magnetic seal mechanism in which a magnetic fluid is retained by using a magnetic circuit formed between an outer ring of the bearing and a magnet provided on a side of the bearing.
Japanese Patent Application Publication No. 2013-110 (the “110 Publication”) discloses a fishing reel in which a drive shaft that is rotated by handle operation is rotatably supported by a magnetic fluid sealed bearing in which a magnetic fluid seal is provided integrally with the bearing.
However, in the sealed bearing structure of the '97 Publication, only one side of the bearing is magnetically sealed so that seawater could penetrate through a fitting portion between an inner ring of the bearing and the supporting shaft, a fitting portion between an outer ring of the bearing and the line roller, and a portion where a screw is clamped. The seawater in the bearing may degrade smoothness of the bearing and therefore the sealing structure of the '97 Publication is not sufficient for a support member of a fishing line guide used in a harsh environment.
Moreover, in the sealed bearing structure of the '97 Publication, the magnetic seal mechanism is arranged adjacent to the side of the bearing so that it can be troublesome to handle it and to perform maintenance. In addition, because only the one side of the bearing is magnetically sealed, both sides of the inner ring are pressed toward the shaft in order to enhance a waterproof property. Accordingly a shear force in the axial direction works on the inner and outer rings of the bearing, and an excessive force could work on the bearing, which slows rotation of the line roller.
Whereas in the sealed bearing structure of the '110 Publication, the drive shaft that is rotated by handle operation is rotatably supported by the magnetic fluid sealed bearing in which the magnetic fluid seal is provided integrally with the bearing so that it can be easy to handle and to perform maintenance. However, this sealing is only for the bearing that supports the drive shaft rotated by the handle operations and is not for a bearing of a rapidly-rotating line roller that imparts a strong tension to a fishing line to guide the fishing line to the spool. Moreover, like the one disclosed in the '97 Publication, since only the one side of the bearing is magnetically sealed so there is the same drawback as the one described above with reference to the '97 Publication.